I think the Complete Story of the Gender Pay Gap is still to be written. Claudia Goldin's knowledge and experience in this field is amazing. It is part of the story but I think there is more to be added. We probably will not know everything about the gender pay gap until we succeed at closing it.
In order to close the ambition gap, however, those who already hold positions of power, and are frustrated with the lack of young women excelling at work, will have the next move, guiding us as we take our first steps into the workforce.
Negotiating your salary shows your employer that you are capable, confident and comfortable with what you have to offer. Those skills are the ones your employer will value when it comes to increasing your level of responsibility, trusting you with clients and promoting you.
Linda Babcock herself, the author of the studies that gave rise to the "women don't ask" industry, has shown that women don't negotiate for a very simple reason: they sense -- correctly -- that it will hurt them if they do.